Porphyrinâpeptide conjugates bearing multiple nuclear localization sequences (NLS) could show increased tumor cell uptake and affinity for nuclear receptors, and consequently increased photodynamic activity. Previous studies suggest that an increase number of NLS might enhance the nuclear uptake of proteins and other macromolecules. We report the syntheses and investigation of a series of multimeric porphyrinâNLS conjugates bearing two, three or four peptides with the minimum sequence PKKKRKV, linked via PEG or 5-carbon linkers, and with different distributions at the porphyrin periphery. Our results show that the tumor cell uptake and phototoxicity of these conjugates is mainly determined by their amphiphilic character, and not the number of NLS residues per molecule, contrary to previous studies. The mono- and di-substituted photosensitizers bearing one or two PEG linkers and up to three peptide sequences were found to be the most phototoxic toward human carcinoma HEp2 cells, while the tetra-NLS conjugates symmetrically substituted around the porphyrin ring accumulated the least within cells and were non-phototoxic. All conjugates localized intracellularly within endosomal vesicles and lysosomes, probably as a result of an endocytic mechanism of uptake; as a consequence no nuclear uptake was detected by fluorescence microscopy.
含有多个核定位序列 (NLS) 的
卟啉-肽缀合物可能显示出增加的肿瘤细胞摄取和亲核受体能力,从而增强光动力活性。先前研究表明,NLS 数量的增加可能会增强蛋白质和其他大分子的核摄取。我们报道了一系列含有两个、三个或四个最小序列为PKKKRKV的肽的多聚
卟啉-NLS缀合物的合成和研究,这些缀合物通过 P
EG 或五碳连接体连接,并在
卟啉外围具有不同的分布。我们的结果表明,这些缀合物的肿瘤细胞摄取和光毒性主要取决于它们的亲疏
水性,而不是每个分子中 NLS 残基的数量,这与之前的研究相反。含有一个或两个 P
EG 链接体和最多三个肽序列的单取代和二取代光敏剂对人类癌细胞 HEp2 最具光毒性,而四取代 NLS 結合物在
卟啉环上对称地取代,在细胞内积累最少且无光毒性。所有缀合物都定位在细胞内囊泡和溶酶体中,可能是由于内吞机制的摄取结果;因此,荧光显微镜未检测到核摄取。